It’s a challenge to describe Gernot Minke’s home and surrounding neighborhood to a taxi driver, much less convince the driver to stop upon finding the street. That’s because Gernot’s home is barely visible from the street, and it looks like a large mound of dirt covered in grass and flowers. The hobbit-like entrance is the only clue that someone lives here.
This quiet suburb of Kassel, Germany, is home to architect, artist, professor, and author Gernot Minke. On this lovely spring day, Gernot’s garden is bustling with birds, and the small pond outside is teeming with life. The plants in the surrounding landscape blend with the mix of grasses and flowers covering the roof, making it difficult to determine where the ground ends and the roof begins. The entire ecosystem is reaping the benefits of Gernot’s sod roof.
Gernot’s home is part of a district that was once considered undesirable because of its proximity to small industry, so the city readily supported Gernot’s proposal to redesign and green the area—a model for ecological development—in the early 1990s. Codes require that all homes built in the neighborhood have grass or sod roofs; fences are prohibited—only natural landscape barriers can be constructed; roads can’t be sealed to ensure that rain doesn’t run off; and cars must be parked in an area away from the houses. The result is a lush oasis in the middle of suburbia. The housing development is hardly discernable from a distance even though there are thirty-five residences, mostly single-family homes.
Inside Gernot’s understated entry, the space opens into a voluminous, light-filled dome rising thirteen feet high. Clay bricks circle around, layer upon layer, up to a glass skylight. From this central dome, the 216-square-meter home includes six other domed rooms, two framed with timbers, and four clay-constructed variations. The floor plan, resembling a honeycomb design, is a sculpture in every sense of the word. Gernot’s twenty-seven years of studying and experimenting with earth construction have produced a place that not only complements the environment but is also truly part of it.
Many people associate earth building with arid climates, but Gernot has developed a formula that works in central Germany’s damp climate. Key to this formula is a grass roof consisting of a layer of rock-wool thermal insulation, a water- and root-resistant skin, a light substratum, and a top layer of earth and lava, ideal soil in which to grow his grasses and flowers. This layer provides thermal insulation and protects the loam from the elements while providing the necessary vapor diffusion to regulate the humidity.
Gernot, a professor at the University of Kassel and director of the Research Laboratory for Experimental Building, is widely regarded as the European expert on clay and earth construction. He has been heading the research program at the university for twenty-seven years, guiding students as they build experimental dwellings on campus and off. He stresses that earth is a cheap, healthy, nonpolluting building material that is readily available in most parts of the world. Gernot’s book, The Earth Construction Handbook (WIT Press, 2000), is the bible of contemporary earth construction, and more than 1,800 people have attended his intensive workshops and courses.
Gernot’s art of clay construction takes on a new meaning in both his bathroom and sunroom, where he coiled clay so that it snakes around the rooms to form the walls. The use of clay in bathrooms is not only a visual treat, but Gernot asserts it has hygienic benefits, too. Mirrors in a tiled bathroom fog up after a hot shower and take anywhere from thirty to sixty minutes to clear in a closed room. In contrast, mirrors in a bathroom with loam walls in similar conditions take three to six minutes to clear because the clay walls absorb humidity when it’s higher than about 50 percent, and they release it later when the humidity falls below 50 percent.
Gernot developed the unique coil design in the bathroom, in which he feeds lightweight loam through a pump or a funnel into a cotton hose. The cotton hose is tied off and gently squeezed so the loam oozes out and forms a thin layer over the fabric. When stacked, these hoses adhere together and can easily be shaped into sculptural designs.
The wattle and daub method used in Gernot’s sunroom is another time-tested method of mud construction, probably older than using earthen blocks. Loam, usually mixed with straw or fibers, is thrown or pressed onto a structure of vertical and horizontal members. Although extremely labor intensive, the wattle and daub method has been widely used throughout the world.
Most of Gernot’s unfired clay walls have no finish, but in the library he used a lime and casein, or quark, wash. Quark, obtained when rennet from young cows is added to skim milk, is readily available in German grocery stores and resembles something between yogurt and cottage cheese. The lime reacts with casein and forms a chemical waterproofing agent.
An earthen womb
When he’s not teaching at the university, Gernot works in his office and architecture studio at home. He recently completed a thirty-six-foot dome kindergarten, and teachers there are marveling at the structure’s positive affect on children. Gernot has experienced the same effect from living in his own dome, which he likens to an earthen womb. “The connection to the sky within the dome is inspirational,” he says. “It also gives me a feeling of peace and security.”
Beyond his artistic building, Gernot finds time to create paintings inspired by dream images and influenced by Native American art. His paintings grace the clay walls throughout the house, adding a colorful and spiritual dimension.